Back when I had a relapse that lead to my diagnosis I had pretty severe neck pain that made me nauseated and unable to eat or sleep much for at least two weeks. An x-ray showed some cervical stenosis, which is probably still there. I had bad balance problems and trouble walking at the time. Those symptoms have gone away and I wonder whether the pain in my neck at the time was due to MS or I simply strained it because I was struggling so hard for balance, that perhaps I overcompensated and "snatched" my neck to keep from falling over. The neuro gave me simple neck exercises to do for cervical strain to do (I still do them almost daily) and the neck problem eased away. After I got better from the relapse I pretty seriously tweaked one knee doing Tai Chi and seemed to keep re-injuring it for months - the problem was definitely in the joint, because it still makes noise when I bend and straighten the knee. So that is definitely a nonMS thing.
I bring this all up because I think if we are experiencing problems with balance, judging distance when making a step, etc. it can set us up for a physical injury to a joint or neck or back that aren't from MS, at least not directly. There's also a lot of people that don't have MS that step off curbs, etc. and wind up with a pretty bad back injury!
I'm not a doc, but based on the imaging from your chiropractor I would recommend getting copies of that latest MRI and going back to the neuro or an orthopedic doc to show them, because it sounds like at least the lower back and hip pain might be your lower disk that might have got knocked awry when you stepped in the hole. If so, maybe something could be done to relieve that, either surgery or physical therapy or something. I sure hope so! I think you're right to question whether all your spine, hip and leg problems are "simply MS" or not. I had a PA tell me, "just because you hear hoofbeats, it doesn't mean they are always zebras. Sometimes they are just horses."
There are some other posts on this site where people have discussed observed links between physical spinal injuries and subsequent MS cord lesions, which is another angle on your symptoms. I can't remember where that is at.
Maybe someone will see this post and point you to it.